okay i just got pulled over on a 40mph street. the cop clock me at 50mph. but I was doing 42mph. does putting on 18" wheels on your S. Make that big of a difference than 16"?? if show does anyone know the ratio of speed?

 

Knowing the size of your wheels is meaningless unless we know the size of your tires.

 

hehehe......cho nay chet di!!!!
But to be seriously the answere is YES but NOT 42mph=50mph just because ya have the 18s. More like 42mph=44 or 45mph with the 18s. ya can go on any wheels website and recalculate the wheel size and speed.

Ok, i just went into nzowheels.com to calculated your tire-wheel ratio for ya:
16" stock---tire height is 23.97" and total circumference is 75.31"
18" wheel&tire----tire height is 24.75" and circumference is 77.76"
the different is 2.45" or 3.25%...that means that if ya are driving @70mph=72mph on your 18s with 245-35-18

 

invest in the yellow box. hahah

yellow box

 

http://www.miata.net/garage/tirecalc.html

Use 245/45-16 for the stock tire size.